汞镉对水稻叶片光合作用的影响

栽培在Cd浓度0,0.01、0.05、0.1、1、5ppm和Hg浓度0、0.1、0.5、1、3、5ppm的荷格兰德溶液中的水稻,其叶片光合强度随处理浓度和叶片金属含量增加而明显地下降。用不同浓度Cd、Hg处理的植株,在拔节期光合比率(即处理叶片光合强度为对照叶片光合强度的百分比,下同)分别减少17—43%和22—66%。到了盛花期,各处理叶片光合比率有所提高,低浓度处理的尤为显著,这是成年植株对重金属逐渐产生抗性的结果。Cd使叶片逐渐褪绿,破坏叶绿素结构;Hg抑制根系正常生长,妨碍水分吸收,从而抑制光合作用。初步看出在光合比率约减少50%时,叶片的表面伤害巳很突出,可达到严重受害的界限。光合比率下降导致了产量及千粒重的降低。

EFFECT OF MERCURY AND CADMIUM ON PHOTOSYNTHESIS OF THE RICE LEAVES

Rice was grown in Hoagland solution added separately with Cd at 0, 0.01,0.05,0.1, l,5ppm and Hg at 0, 0.1, 0.5, 1, 3, 5ppm. Photosynthesis of the leaves was found decreased sharply as the enriched concentration in the solution and the content of heavy metals in the leaves increased. During the jointing stage, the rates of photosynthesis of rice expressed in percentage of photosynthesis of the leaves being treated with respect to controls, treated with different concentrations of cadmium and mercury, were reduced to 17-43%and 22-66%respectively. During the full blooming stage, the rates of the photosynthesis for all of the leaves being treated were on the rise, particularly so for those being treated at low concentrations. And it may be explained of owing to the fact that resistance resulted from adaptation of the rice to the heavy metals absorbed. Cd gradually caused the leaves chlorosis and damaged the chlorophyll; while Hg inhibited the normal growth of the roots and hindered absorption of water, thus affecting photosynthesis. Preliminary observations showed that in case the photosynthesis rates were reduced to about 50%, the surface of the leaves carried clear marks of reaching the point of severe injury. Therefore, lowering of the photosynthesis rates may lead to reduction of the yield and thousand kernels weight of the rice.